Spodumene Pegmatites and Related Leucogranites from the AustroAlpine Unit (Eastern Alps, Central Europe): Field Relations, Petrography, Geochemistry, and Geochronology

Research Article| October 23, 2018 Spodumene Pegmatites and Related Leucogranites from the AustroAlpine Unit (Eastern Alps, Central Europe): Field Relations, Petrography, Geochemistry, and Geochronology Tanja Knoll; Tanja Knoll § Geological Survey of Austria, Neulinggasse 38, 1030 Vienna, Austria § Corresponding author e-mail address: tanja.knoll@geologie.ac.at Search for other works by this author on: GSW Google Scholar Ralf Schuster; Ralf Schuster Geological Survey of Austria, Neulinggasse 38, 1030 Vienna, Austria Search for other works by this author on: GSW Google Scholar Benjamin Huet; Benjamin Huet Geological Survey of Austria, Neulinggasse 38, 1030 Vienna, Austria Search for other works by this author on: GSW Google Scholar Heinrich Mali; Heinrich Mali Department of Applied Geosciences and Geophysics, Montanuniversität Leoben, Peter-Tunnerstraße 5, 8700 Leoben, Austria Search for other works by this author on: GSW Google Scholar Peter Onuk; Peter Onuk Department of Applied Geosciences and Geophysics, Montanuniversität Leoben, Peter-Tunnerstraße 5, 8700 Leoben, Austria Search for other works by this author on: GSW Google Scholar Monika Horschinegg; Monika Horschinegg Department of Lithospheric Research, Geocenter, University of Vienna, Althanstraße 14, 1090 Vienna, Austria Search for other works by this author on: GSW Google Scholar Andreas Ertl; Andreas Ertl Institut für Mineralogie und Kristallographie, Geocenter, University of Vienna, Althanstraße 14, 1090 Vienna, Austria Search for other works by this author on: GSW Google Scholar Gerald Giester Gerald Giester Institut für Mineralogie und Kristallographie, Geocenter, University of Vienna, Althanstraße 14, 1090 Vienna, Austria Search for other works by this author on: GSW Google Scholar Author and Article Information Tanja Knoll § Geological Survey of Austria, Neulinggasse 38, 1030 Vienna, Austria Ralf Schuster Geological Survey of Austria, Neulinggasse 38, 1030 Vienna, Austria Benjamin Huet Geological Survey of Austria, Neulinggasse 38, 1030 Vienna, Austria Heinrich Mali Department of Applied Geosciences and Geophysics, Montanuniversität Leoben, Peter-Tunnerstraße 5, 8700 Leoben, Austria Peter Onuk Department of Applied Geosciences and Geophysics, Montanuniversität Leoben, Peter-Tunnerstraße 5, 8700 Leoben, Austria Monika Horschinegg Department of Lithospheric Research, Geocenter, University of Vienna, Althanstraße 14, 1090 Vienna, Austria Andreas Ertl Institut für Mineralogie und Kristallographie, Geocenter, University of Vienna, Althanstraße 14, 1090 Vienna, Austria Gerald Giester Institut für Mineralogie und Kristallographie, Geocenter, University of Vienna, Althanstraße 14, 1090 Vienna, Austria § Corresponding author e-mail address: tanja.knoll@geologie.ac.at Publisher: Mineralogical Association of Canada First Online: 23 Oct 2018 Online Issn: 1499-1276 Print Issn: 0008-4476 © 2018 Mineralogical Association of Canada The Canadian Mineralogist (2018) 56 (4): 489–528. https://doi.org/10.3749/canmin.1700092 Article history First Online: 23 Oct 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Tanja Knoll, Ralf Schuster, Benjamin Huet, Heinrich Mali, Peter Onuk, Monika Horschinegg, Andreas Ertl, Gerald Giester; Spodumene Pegmatites and Related Leucogranites from the AustroAlpine Unit (Eastern Alps, Central Europe): Field Relations, Petrography, Geochemistry, and Geochronology. The Canadian Mineralogist 2018;; 56 (4): 489–528. doi: https://doi.org/10.3749/canmin.1700092 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyThe Canadian Mineralogist Search Advanced Search Abstract In the Eastern Alps (Central Europe), about two dozen spodumene pegmatite bodies extend heterogeneously over the Austroalpine Unit. They are spatially associated with leucogranites and simple pegmatites formed during the Permian extensional event. The pegmatites and leucogranites were overprinted during the Alpine orogeny with different intensities, leading to various structural and chemical changes to the magmatic features. The magmatic assemblage consists of K-feldspar, quartz, plagioclase, muscovite, garnet, and tourmaline, with additional spodumene in the pegmatites. Beryl is rarely present and other accessory phases such as apatite, cassiterite, or Nb-Ta phases are exceptional. Mineral compositions indicate that the magmatic garnet is rich in Mn and Fe and has Ca-rich and Mn-poor Alpine metamorphic overgrowths. Sm-Nd ages of carefully separated crystals of magmatic garnet from the leucogranites and spodumene pegmatites fall in the range of 245–280 Ma. These Permian-Early Triassic ages are in good agreement with previously published results from associated simple pegmatites. Tourmalines from spodumene pegmatites belong to the elbaite–schorl series, with an unusual but significant dravite component. The occurrence of tourmaline and the absence of biotite may be due to the low Ti content (<0.06 wt.% TiO2) in the melt of both rock types. Trace-element compositions (Rb, Li, Cs, Tl, or Ba) of magmatic muscovite show that the leucogranites and spodumene pegmatites belong to the same fractionation trend, with more fractionated signatures in the spodumene pegmatites. Whole-rock geochemical compositions indicate that both lithologies have a common peraluminous granitic geochemistry, similar minor- and trace-element distribution patterns, and share a fractionation trend of trace elements including Be, Li, Rb, Cs, Sn, Ge, Ba, and REE. Positive and negative Eu anomalies in analyzed leucogranites and spodumene pegmatites, respectively, are interpreted to be due to the extraction of Eu in plagioclase crystallizing in leucogranite during the melt evolution. Values of ε(t)Nd (approximately –8) and initial 87Sr/86Sr ratios (0.7098–0.7353) indicate a crustal origin for the primary melts. Using the Permian metamorphic conditions of the country rock as a proxy, the spodumene pegmatites intruded at more than 10 km depth at somewhat higher structural levels than the leucogranites. This set of field and petrographic observations as well as geochemical and geochronological data suggest that the leucogranites and spodumene pegmatites of the Austroalpine Unit are contemporaneous and cogenetic, whereby the spodumene pegmatites show a higher degree of chemical evolution and concentration of rare metals. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.